The sequence and mechanism of assembly of the mitochondrial ATPase will be studied in yeast during adaptation of cells from a glucose repressed to depressed state. Mitochondrially synthesized subunit proteins of the ATPase will be purfied and characterized for their lipid content and amino acid composition. The hypothesis that mitochondria do not synthesize proteins in toto but rather append a polypeptide unit to a preexisting cytoplasmically made protein will be tested. The role of proteolipids as structural subunits of mitochondrial enzyme complexes such as the ATPase, cytochrome oxidase and coenzyme Q-cytochrome c reductase will be examined. A low-molecular weight subunit of the ATPase with the properties of a proteolipid will be studied from the standpoint of its function and possible involvement in the conferral of oligomycin-sensitivity. The possibility that this subunit forms a phosphorylated intermediate of the enzyme will also be investigated.